hypocellular

Hypocellular is an adjective used in medical and scientific contexts to describe tissue that contains fewer cells than are typical for that tissue in a given age or species. It is often used to refer to bone marrow but can apply to other tissues where cellular density is reduced. The term is usually determined by histological examination or imaging that estimates the proportion of cells occupying the tissue.

In bone marrow, hypocellularity means a reduced proportion of hematopoietic (blood-forming) cells relative to the supporting stroma and fat. In adults, normal marrow cellularity typically ranges around 30-70% in the biopsy specimen, with lower percentages expected in older individuals. Hypocellular marrow is characterized by sparse hematopoietic elements and increased adipose (fat) spaces. This pattern is assessed by pathologists on bone marrow biopsy and is distinguished from hypercellular marrow, where there is an excess of hematopoietic cells.

Clinically, hypocellular marrow can lead to cytopenias—anemia, low platelets, and/or low white blood cells—because hematopoietic activity is diminished. Causes include aplastic anemia and other marrow-suppressive conditions, prior chemotherapy or radiation, infections, autoimmune processes, and certain myelodysplastic syndromes. The prognosis and treatment depend on the underlying cause and the degree of cellularity loss; management may range from supportive care to disease-directed therapies or marrow transplantation in selected cases.

Outside the marrow, hypocellular can describe tissues with abnormally low cellular density compared with normal anatomy; the assessment is always relative to the tissue type and the patient’s age. Overall, the term conveys a reduced cellular component within a tissue compartment.